RAMAN AND PHOTOLUMINESCENCE STUDIES ON THERMALLY ANNEALED POROUS SILICON

We report Raman and Photoluminescence (PL) studies of porous silicon (PS) as a function of isochronal thermal annealing from room temperature to 900 degrees C. The PL peak position and intensity show nonmonotonic variation with increasing temperature. The PL intensity first increases upto 100 degrees C, then decreases till 550 degrees C and recovers its intensity at 700 degrees C before it completely disappears at 800 degrees C. The red shifted asymmetric raman line shape can be fitted by phonon confinement model along with the disordered silicon component. Our results clearly indicate that the origin of visible PL can be better explained by a new hybrid model which incorporates both nanostructures for quantum confinement and silicon complexes (such as SiHx and siloxene) and defects at Si/SiO2 interfaces as luminescent centres.